Re: Modifying TOAST thresholds

Gregory Stark <stark(at)enterprisedb(dot)com> writes:
> "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
>> I also think that we ought to add TOAST_MAX_CHUNK_SIZE to the set of
>> compiled-in parameters that are recorded in pg_control and checked for
>> compatibility at startup (like BLCKSZ) --- this will prevent anyone from
>> shooting themselves in the foot while experimenting.

> Is there any reason to experiment with this? I would have thought we would
> divorce TOAST_MAX_CHUNK_SIZE from TOAST_THRESHOLD and hard code it as the same
> expression that's there now. Ie, the largest size that can fit in a page.

No, right now it's the largest size that you can fit 4 on a page. It's
not obvious to me that 4 is optimal once it's divorced from TOAST_THRESHOLD.
It seems possible that the correct number is 1, and even if it's useful
to keep the tuples smaller than that, there's no reason to assume 4 is
the best number per page.

regards, tom lane